Gold is used in a variety of industrial applications, both because of its pleasing luster and excellent electrical properties. In particular, it is extensively used as an electrical contact material because of its chemical stability and the fact that an insulating layer is not formed on the surface.
Because of the extensive use of gold and its increasing cost, considerable amount of work is being devoted towards improving gold electroplating processes. In particular, increased efficiency and plating speed is highly desirable. In most gold plating procedures, the gold is added in the form of a solution (i.e., a solution of Au(CN).sub.2.sup.-) and the anode is non-consumable. In these procedures, the anode electrolyzes water with the formation of gaseous oxygen. Reducing the electrochemical potential for the electrolysis of oxygen is important for several reasons. First, it increases the efficiency of the process by reducing power consumption. Second, it reduces or eliminates a number of side reactions which are undesirable in the gold plating process. For example, reduction or elimination of the formation of trivalent gold is highly desirable. Trivalent gold reduces the efficiency of the gold plating process and makes uncertain predictions of gold plating thickness from plating current measurements. Reduction of the electrochemical potential for the electrolysis of water is often critical in maintaining a commercially viable high speed gold plating operation.
A variety of anodes have been described in the literature. Particular references are the following: U.S. Pat. No. 3,428,544 (Guiseppe Bianchi et al, issued Feb. 18, 1969); U.S. Pat. No. 3,491,014 (Guiseppe Bianchi et al, issued Jan. 20, 1970); U.S. Pat. No. 3,616,445 (Guiseppe Bianchi, issued Oct. 26, 1971); and Extended Abstracts of the Electrochemical Society Spring Meeting, Seattle, Washington, May 21-16, 1978, Volume 78-1, pps. 1202-1205. Also, a recently issued patent (U.S. Pat. No. 4,067,783 issued Jan. 10, 1978, Okinaka, et al) describes anodes useful in gold plating.